1. Technical Field
The present invention relates to an optical amplifying glass. Particularly, it relates to a broad band optical amplifying glass operable in a wavelength region of from 1.55 to 1.65 xcexcm.
2. Background Art
For the purpose of application to an optical communication field, there have been research and development of an Er-doped optical fiber amplifier (EDFA) wherein an optical fiber having Er (erbium) doped to the core is used as an optical amplifying medium, and application to an optical communication system is actively pursued. On the other hand, to cope with diversification of communication services expected in future, a wavelength division multiplexing communication system (WDM) has been proposed to increase the transmission capacity. The transmission capacity will increase, as the number of wavelength division multiplexing channels increases. Application of EDFA to such a wavelength division multiplexing communication system is also being studied. As EDFA presently proposed, an Er-doped quartz type fiber or an Er-doped fluoride fiber, is known.
In the case of the Er-doped quartz type fiber which has heretofore been known, the wavelength dependency of gain is sharp, and the wavelength width wherein an adequate gain can be obtained, is narrow at a level of from 10 to 30 nm. As a result, the number of wavelength division multiplexing channels, is limited to a level of from 30 to 40 channels, so long as conventional EDFA is used.
If EDFA showing a flat gain within a wider wavelength region, can be realized, the useful signal wavelength can be broadened, and substantial improvement in the transmission capacity can be expected. Thus, realization of such EDFA is desired.
In order to solve such a problem, an optical amplifier has been proposed which can be used in a wide wavelength region by arranging amplifiers differing in the amplification gain characteristics to wavelength, in series or in parallel. However, there have been problems that the structure tends to be complex, and that there is a region where no amplification is possible in the vicinity of the center of the wavelength region. Further, JP-A-8-110535 proposes a tellurite oxide type glass as a glass capable of amplification in a broad band. However, the tellurite type glass usually has a low glass transition point and is thermally unstable. In order to improve the amplification gain of an optical amplifier, it is necessary to introduce a high intensity exciting laser beam into glass, whereby thermal damages are likely to be brought about by the high intensity laser beam.
An object of the present invention is to solve the above problems and to provide an optical amplifying glass which has a high glass transition point and which has a large wavelength width wherein the gain is obtainable.
The present invention provides an optical amplifying glass which comprises a matrix glass having Er doped in an amount of from 0.01 to 10% as represented by mass percentage, wherein the matrix glass consists essentially of, as represented by mol % based on the following oxides:
wherein the total of contents of B2O3 and SiO2 is from 5 to 75 mol %, and the total of contents of Ga2O3, WO3 and TeO2 is from 0.1 to 35 mol %, and contains substantially no CeO2 (first invention).
Further, it provides such an optical amplifying glass, wherein the matrix glass consists essentially of, as represented by mol % based on the following oxides:
wherein the total of contents of B2O3 and SiO2 is from 10 to 55 mol %, the total of contents of Ga2O3, WO3 and TeO2 is from 5 to 35 mol %, and the total of contents of SiO2 and TeO2 is from 10 to 45 mol %, and contains substantially no CeO2 (second invention).
Further, it provides a production method for an optical amplifying glass, which is a method for producing the optical amplifying glass of the second invention by melting raw materials, wherein the temperature for melting the raw materials for the optical amplifying glass is at most 1,200xc2x0 C.